In recent years, with the increasing integrated level and rapidly increasing functions of the equipment applied in the optical system, the optical system is required to be more accurate, lighter and smaller. In order to meet the refractive index of 1.74 to 1.80 and Abbe number of 47 to 51, the optical glass is often B2O3—La2O series. Japanese patent application laid-open No. 2006-117506 discloses an optical glass with refractive index of 1.74-1.80 and Abbe number of 47-51. However, the optical glass contains 25-35% (by wt %, hereinafter the same) of Gd2O3. Gd2O3 is rare earth oxide and expensive so that the optical glass is featured in high cost.